Known methods for decorating injection-molded products etc. include a simultaneous injection molding-lamination method and a simultaneous injection molding-transfer method, in each of which a printed sheet is placed in an injection mold and a molding resin is injection-molded to produce a molded product with a surface coated with the printed sheet. These methods generally include integrally molding the injection molding resin with the sheet so that a printed layer is disposed on the back side (injection molding resin side) of the substrate sheet, thereby producing a molded product having a flat surface and a uniform glossy appearance and failing to provide a surface of the molded product with a feeling of concave-convex patterned design.
Examples of the concave-convex patterned design include a design having a surface with a concave-convex pattern which can be felt visually and tactilely and a design having a flat surface with a visible concave-convex pattern (depth feel).
A known method for producing an injection-molded product having a concave-convex patterned surface includes previously forming fine crimps, which form projections and depressions, on a cavity surface of an injection mold, thereby forming projections and depressions on a surface of the injection-molded product. However, this method has the problem of increasing cost due to the need to form projections and depressions on each mold and difficulty of injecting the injection molding resin into the fine crimps, thereby causing difficulty in accurately reproducing fine projections and depressions and in conforming the projections and depressions to a print pattern.
There is also a known method of forming projections and depressions, in which a shaping sheet or a shaping film is placed in an injection mold and then separated after injection molding, the shaping film being produced by curing a photocurable resin composition using, as a mold, a metal stamper plate or a shaping sheet having projections and depressions which are previously physically formed on a surface thereof by press-contact of a heated engraved roll for embossing or schreinerizing (refer to, for example, Patent Literature 1). However, the shaping sheet having projections and depressions physically formed thereon has the problem that embossed portions are plastically deformed by orientation returning when exposed to a high resin temperature during injection molding, failing to create desired projections and depressions. In addition, the method uses an embossing apparatus or a stamper plate, and thus the plate is required to be remade according to the concave-convex pattern. Further, since projections and depressions are imparted in the sheet forming process, the projections and depressions have been produced in a wound state, thereby easily causing weaving defect and gauge band defect due to overlapping of projecting portions. This results in the problem of requiring careful handling.
On the other hand, examples known as the injection-molded product having a smooth surface but also having a visible concave-convex pattern (depth feel) includes those disclosed in Patent Literatures 2 and 3. The method of Patent Literature 2 has the need to prevent embossed portions from disappearing by injection molding pressure and thus includes embossing a film, filling embossed depressions with a resin such as an acryl resin, and integrating the film with a molding resin by injection molding. However, this method includes the step of embossing the sheet and the step of applying the resin to the sheet, thereby complicating the process. In addition, the method of Patent Literature 3 includes embossing a laminate which contains a transparent resin base sheet and a photoluminescent layer to form a high-gloss region and a low-gloss region in a surface of the transparent resin base sheet and to form thick and thin regions in the transparent resin base sheet corresponding to the high-gloss region and the low-gross region, and then integrating the sheet with a molding resin by injection molding. However, this method has the problem of the need to conform the high-gloss and low-gloss regions formed by printing to the embossed portions, and thus an unusual technique is required for completely conforming print regions to projections and depressions of a design which requires a fine pattern.
These methods require the embossing apparatus and have the need to remake the plate according to the concave-convex pattern.